Lunar Lawn Mower

November 9, 2005: "If you can't lick 'em, join
'em," goes a cliché that essentially means "figure
out how to live with whatever you can't get rid of."

That
may be superb advice for living and working on the moon.

Scientists
and engineers figuring out how to return astronauts to the
moon, set up habitats, and mine lunar soil to produce anything
from building materials to rocket fuels have been scratching
their heads over what to do about moondust. It's everywhere!
The powdery grit gets into everything, jamming seals and abrading
spacesuit fabric. It also readily picks up electrostatic charge,
so it floats or levitates off the lunar surface and sticks
to faceplates and camera lenses. It might even be toxic.

So
what do you do with all this troublesome dust? Larry Taylor,
Distinguished Professor of Planetary Sciences at the University
of Tennessee has an idea:

"I'm
one of those weird people who like to stick things in ordinary
kitchen microwave ovens to see what happens," Taylor
confessed to several hundred scientists at the Lunar Exploration
Advisory Group (LEAG) conference at NASA's Johnson Space Center
last month.

At
home in Tennessee, his most famous experiment involves a bar
of Irish Spring soap, which quickly turns into "an abominable
monster" when you hit the microwave's Start button. But
that's not the one he told about at LEAG.

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Apropos
to the moon, he once put a small pile of lunar soil brought
back by the Apollo astronauts into a microwave oven. And he
found that it melted "lickety-split," he said, within
30 seconds at only 250 watts.

The
reason has to do with its composition. The lunar regolith,
or soil, is produced when micrometeorites plow into lunar
rocks and sand at tens of kilometers per second, melting it
into glass. The glass contains nanometer-scale beads of pure
iron – so called "nanophase" iron. It is those tiny
iron beads that so efficiently concentrate microwave energy
that they "sinter" or fuse the loose soils into
large clumps.

This
observation has inspired Taylor to imagine all kinds of machinery
for sending to the moon that could fuse lunar dust into useful
solids.

"Picture a buggy pulled behind a rover that is outfitted
with a set of magnetrons," that is, the same gizmo at
the guts of a microwave oven. "With the right power and
microwave frequency, an astronaut could drive along, sintering
the soil as he goes, making continuous brick down half a meter
deep--and then change the power settings to melt the top inch
or two to make a glass road," he suggested.

Right:
Prof. Larry Taylor's cartoon-sketch of a "lunar lawnmower."

"Or
say that you want a radio telescope," he continued. "Find
a round crater and run a little microwave 'lawnmower' up and
down the crater's sides to sinter a smooth surface. Hang an
antenna from the middle--voila, instant Arecibo!" he
exclaimed, referring to the giant 305-meter-diameter radio
telescope in Puerto Rico formed out of a natural circular
valley.

Technical
challenges remain. Sintering moondust in a microwave oven
on Earth isn't the same as doing it on the airless moon. Researchers
still need to work out details of a process to produce strong,
uniformly sintered material in the harsh lunar environment.

But
the idea has promise: Sintered rocket landing pads, roads,
bricks for habitats, radiation shielding--useful products
and dust abatement, all at once.